Creating the shape of an image button is similar to an image

Question

I am using android API 1.5 and trying to make some images for the user to click. Images have very random shapes. When I put images on the image button, the button itself is always rectangular. therefore, you can click the button without clicking the actual image. I want the user to click an image to click a button, instead of clicking a blank spot on the button and still pressing the button.

Is there a way to make the clickable area of ​​the image button am match the random image?